JP7202769B2 - Encoding device, decoding device and program - Google Patents

Description

The present invention relates to an encoding device, a decoding device and a program.

H.265/HEVC (High Efficiency Video Coding)
In the moving image (video) coding method represented by , prediction is performed while switching between two types of prediction, inter prediction using temporal correlation between frames and intra prediction using spatial correlation within a frame. After generating a difference signal, it is configured to output a stream obtained by performing orthogonal transform processing, loop filter processing, and entropy coding processing.

In intra prediction in HEVC, a total of 35 predictions such as Planer prediction, DC prediction, and directional prediction
Various modes are prepared, and intra prediction is performed using adjacent decoded reference pixels according to the mode determined by the encoder.

Here, in intra prediction, a specified value (10 It is configured to create reference pixels to be used when generating a predicted image by filling in "512" in the case of a bit moving image).

In addition, in conventional HEVC, encoding processing is performed in raster scan order from the upper left, so there are cases where reference pixels have not been decoded. In such a case, a prediction image is generated using a value obtained by extrapolating the nearest decoded reference pixel to the 0th order.

In particular, in intra prediction in conventional HEVC, reference pixels located at the lower left and upper right of the CU have already been decoded by the encoding process in the raster scan order shown in FIG. In many cases, it is not (see FIG. 8B), and in such a case, if directional prediction is performed from the direction in which there is a reference pixel that has not been decoded, the prediction accuracy will decrease, and the coding efficiency will decrease. There was a problem.

In order to solve such a problem, in intra prediction, raster scan order (for example, Z type) is used as the encoding processing order for a plurality of transform blocks existing in a CU (hereinafter referred to as "TU: Transform Unit"). In addition, there is known a technique for improving prediction accuracy by giving flexibility to the order of encoding such as U type and X type (see Non-Patent Document 1).
.

In addition, in the examples of FIGS. 8A and 8B, direction prediction is performed in the direction from the lower left to the upper right (the direction opposite to the direction indicated by the dashed arrows in FIGS. 8A and 8B). The pixel on the dashed arrow is predicted using the lower left reference pixel. In the drawings of this specification, the arrow indicating the direction of the intra prediction mode (prediction direction) is directed from the target pixel for intra prediction to the reference pixel, as described in the HEVC standard (the same applies hereinafter). .

Mochizuki et al., "Applied intra-prediction method based on mean value coordinates", Information Processing Society of Japan research report, vol, 2012-AVM-77, No.12

In conventional HEVC, as shown in FIG. 9, intra prediction is prediction using spatially adjacent upper or left decoded reference pixels, and the accuracy of the predicted image at a position close to the decoded reference pixels is high. Using the fact that the accuracy of the predicted image at a position far from the decoded reference pixels tends to be low, discrete sign transform (hereinafter referred to as "DST") is performed horizontally and vertically from the left side and upper direction where the decoded reference pixels are located. ) or discrete cosine transform (hereinafter referred to as "DCT") is applied to reduce the entropy of the residual signal.

In particular, as shown in FIG. 10, the shape of the impulse response of the DST has an asymmetrical shape with one end closed and the other end widened. Entropy can be effectively reduced by applying DST in accordance with the signal strength of .

As described above, in the technique described in Non-Patent Document 1, there are cases where reference pixels on the lower side or the right side are used in intra prediction.

In such a case, in the residual signal, the signal intensity on the lower side and the right side near the position of the reference pixel tends to be small, and the signal intensity on the upper side and the left side far from the position of the reference pixel tends to be high.
If the orthogonal transform is applied as usual, the entropy may increase, which causes a problem of lowering the coding efficiency.

Therefore, the present invention has been made to solve the above-described problems, and is an encoding method capable of reducing an increase in entropy even when using reference pixels on the lower side or the right side in intra prediction. An object is to provide a device, a decoding device and a program.

A first feature of the present invention is an encoding device that is configured to divide and encode an original image in units of frames that constitute a moving image into encoding target blocks, and uses an intra prediction mode to encode An intra prediction unit configured to generate a predicted image, a residual signal generation unit configured to generate a residual signal from a difference between the predicted image and the original image, and the intra prediction unit , when the predicted image is generated using the reference pixels located on at least one of the right side and the bottom side, the basis of at least one of the horizontal direction and the vertical direction is inverted with respect to the residual signal, and the basis is orthogonal and an orthogonal transform unit configured to perform transform processing.

A second feature of the present invention is a decoding device configured to divide an original image in units of frames constituting a moving image into encoding target blocks and decode the predicted image using an intra prediction mode. an intra predictor configured to generate a
When the predicted image is generated using the reference pixels located on at least one of the right side and the bottom side, inverse orthogonal transform processing is performed on the transform coefficients after inverting at least one of the bases in the horizontal direction and the vertical direction. and an inverse transform unit configured to generate a residual signal by applying.

A third feature of the present invention is an encoding device configured to divide and encode an original image in units of frames constituting a moving image into encoding target blocks, wherein the intra prediction mode is used to encode An intra prediction unit configured to generate a predicted image, a residual signal generation unit configured to generate a residual signal from a difference between the predicted image and the original image, and the intra prediction unit , when the predicted image is generated using the reference pixels located on at least one of the right side and the bottom side, the residual signal is inverted in at least one of the horizontal direction and the vertical direction and then orthogonally transformed. The gist of the invention is to comprise an orthogonal transform unit configured as follows.

A fourth feature of the present invention is a decoding device configured to divide an original image in units of frames constituting a moving image into encoding target blocks and decode the predicted image using an intra prediction mode. an intra predictor configured to generate a
When the predicted image is generated using the reference pixels located on at least one of the right side and the bottom side, a signal obtained by performing inverse orthogonal transform processing on the transform coefficient is inverted in at least one of the horizontal direction and the vertical direction. an inverse transform unit configured to generate a residual signal by

A gist of a fifth feature of the present invention is a program for causing a computer to function as the encoding device according to the above first or third feature.

A gist of a sixth aspect of the present invention is a program for causing a computer to function as the decoding device according to the second or fourth aspect.

Advantageous Effects of Invention According to the present invention, it is possible to provide an encoding device, a decoding device, and a program capable of reducing an increase in entropy even when lower or right reference pixels are used in intra prediction.

FIG. 1 is a functional block diagram of an encoding device 1 according to the first embodiment. FIG. 2 is a diagram illustrating an example of intra prediction when TU partitioning is performed in the first embodiment. FIG. 3 is a flow chart showing the operation of the encoding device 1 according to the first embodiment. FIG. 4 is a functional block diagram of the decoding device 3 according to the first embodiment. FIG. 5 is a flow chart showing the operation of the decoding device 3 according to the first embodiment. FIG. 6 is a flow chart showing the operation of the encoding device 1 according to the second embodiment. FIG. 7 is a flow chart showing the operation of the decoding device 3 according to the second embodiment. FIG. 8 is a diagram for explaining conventional HEVC. FIG. 9 is a diagram for explaining conventional HEVC. FIG. 10 is a diagram for explaining conventional HEVC. FIG. 11 is a diagram for explaining conventional HEVC.

(First embodiment)
An encoding device 1 and a decoding device 3 according to the first embodiment of the present invention will be described below with reference to FIGS. 1 to 5. FIG. Here, the encoding device 1 and the decoding device 3 according to the present embodiment are HE
It is configured to support intra-prediction in moving image coding methods such as VC. Note that the encoding device 1 and the decoding device 3 according to the present embodiment are configured to be compatible with any video encoding method as long as it is a video encoding method that performs intra prediction.

The encoding device 1 according to the present embodiment is configured to divide an original image in units of frames constituting a moving image into CUs and encode the CUs. Further, the encoding device 1 according to the present embodiment has a CU
can be divided into multiple TUs. Hereinafter, in this embodiment, a case in which a CU is divided into a plurality of TUs will be described as an example, but the present invention can also be applied to a case in which a CU is not divided into a plurality of TUs.

Note that, in this embodiment, a CU to be encoded that does not have an adjacent decoded reference pixel, such as the CU located at the upper leftmost position in a frame, is assigned a specified value (for a 10-bit video, "
512”) is configured to generate reference pixels used when generating a predicted image, all pixels adjacent to the left side of the CU to be coded can be used as reference pixels. do.

As shown in FIG. 1, the encoding device 1 according to this embodiment includes an intra prediction mode determination unit 11
, TU division determination unit 12 , encoding order control unit 13 , sequential local decoded image generation unit 14 , memory 15 , and entropy encoding unit 16 .

The intra-prediction mode determination unit 11 is configured to determine the optimum intra-prediction mode to apply to the CU.

The TU partition decision unit 12 is configured to decide whether to partition a CU into a plurality of TUs. In this embodiment, as a method of dividing a CU into a plurality of TUs, a case of 4 divisions is described as an example. , is not limited to such cases.

The coding order control unit 13 is configured to determine the coding order of the TUs within the CU based on the intra prediction mode (for example, the direction of the intra prediction mode).

Specifically, when the TU division determination unit 12 determines to divide a CU into a plurality of TUs, the coding order control unit 13 performs the following operations as shown in FIGS. , when the direction of the intra prediction mode determined by the intra prediction mode determination unit 11 is the direction from the lower left to the upper right (that is, when the direction prediction is performed from the lower left to the upper right), the CU
As the coding order of TUs in the conventional raster scan order (Z type as shown in FIG. 8(a))
TU#A3 (lower left TU in CU#A) → TU#A4 (lower right TU in CU#A
)→TU#A1 (upper left TU in CU#A)→TU#A2 (upper right TU in CU#A), or TU#A3 (lower left TU in CU#A)→ TU#A1 (CU#A
(upper left TU in CU#A) → TU#A4 (lower right TU in CU#A) → TU#A2 (upper right TU in CU#A). may be configured to

Further, the coding order control unit 13 determines that the TU division determination unit 12 determines to divide the CU into a plurality of TUs, and the direction of the intra prediction mode determined by the intra prediction mode determination unit 11 is TU# A2 (upper right TU in CU#A) → TU#A4 (CU#A
lower right TU in CU#A) → TU#A1 (upper left TU in CU#A) → TU#A3 (lower left TU in CU#A), or TU#A2 (in CU#A upper right TU) → TU#
A1 (upper left TU in CU#A)→TU#A4 (lower right TU in CU#A)→TU#A3
It may be configured to adopt a predetermined encoding order among the encoding orders of (lower left TU in CU#A).

The sequential locally decoded image generation unit 14 is configured to generate a locally decoded image (a decoded image for each TU) based on the coding order determined by the coding order control unit 13 and the method of dividing the CU into TUs. ing.

Specifically, when the TU division determination unit 12 determines to divide the CU into a plurality of TUs, the sequential locally decoded image generation unit 14 follows the coding order determined by the coding order control unit 13. , is configured to sequentially generate a locally decoded image.

As shown in FIG. 1, the sequential local decoded image generation unit 14 includes an intra prediction unit 14a, a residual signal generation unit 14b, an orthogonal transform/quantization unit 14c, and an inverse quantization/inverse orthogonal transformation unit 14d. ,
and a locally decoded image generator 14e.

The intra prediction unit 14 a is configured to generate a predicted image using the intra prediction mode determined by the intra prediction mode determination unit 11 . That is, the intra prediction unit 14a is configured to determine the positions of reference pixels used when generating a predicted image.

Specifically, the intra prediction unit 14a divides the CU into a plurality of TUs by the TU partition determination unit 12.
When it is decided to divide into, and as shown in FIGS. 2A to 2D, the direction of the intra prediction mode (prediction direction) is the direction from the lower left to the upper right, TU#A3 (CU
# Lower left TU in A) → TU#A4 (Lower right TU in CU#A) → TU#A1 (CU#A
upper left TU in) → TU #A2 (upper right TU in CU #A), or T
U#A3 (bottom left TU in CU#A)→TU#A1 (top left TU in CU#A)→TU#
It is configured to generate a prediction image in a predetermined coding order among the coding order of A4 (lower right TU in CU#A)→TU#A2 (upper right TU in CU#A). may be

Here, as shown in FIGS. 2(c) and 2(d), the intra prediction unit 14a predicts TU#A1 (upper left TU in CU#A) whose adjacent lower reference pixel is decoded. and TU#A2
For (the upper right TU in CU#A), the predicted image may be generated using the decoded reference pixels adjacent to the left and lower sides.

In addition, in the encoding device 1 according to the present embodiment, the intra prediction unit 14a performs the direction of the intra prediction mode (prediction direction) is from top right to bottom left, then TU#A2 (CU#
A) → TU#A4 (lower right TU within CU#A) → TU#A1 (upper left TU within CU#A) → TU#A3 (lower left TU within CU#A) or TU
#A2 (upper right TU in CU#A)→TU#A1 (upper left TU in CU#A)→TU#A
4 (lower right TU in CU#A) → TU#A3 (lower left TU in CU#A). may be

Here, the intra prediction unit 14a predicts TU#A in which the adjacent right reference pixel is decoded.
For 1 (upper left TU in CU#A) and TU#A3 (lower left TU in CU#A),
The predicted image may be generated using the upper and right adjacent decoded reference pixels.

Alternatively, the intra prediction unit 14a performs TU#A3 (the lower left TU in CU#A)→TU#A
4 (bottom right TU in CU#A)→TU#A1 (top left TU in CU#A)→TU#A2 (
upper right TU in CU#A), or TU#A3 (lower left T in CU#A)
U) → TU#A1 (top left TU in CU#A) → TU#A4 (bottom right TU in CU#A)
→ When a coding order of TU#A2 (upper right TU in CU#A) is used, a TU whose reference pixel adjacent to the upper side has been decoded (the uppermost TU among the divided TU groups TU
, TU#A1 and TU#A2 in the example of FIG. 2) are not in the common intra-prediction direction in CU#A, but the decoded reference pixels adjacent to the left side, the upper side, or the lower side of the TU are used. It may be configured to perform a predefined prediction, such as linear interpolation.

That is, the intra prediction unit 14a may be configured to generate a predicted image using decoded reference pixels that are adjacent in three directions such as the lower side, the left side, and the upper side.

Alternatively, the intra prediction unit 14a may be configured to generate a predicted image using decoded reference pixels that are adjacent in three directions such as the right side, the left side, and the upper side.

The residual signal generation unit 14b is configured to generate a residual signal from the difference between the predicted image generated by the intra prediction unit 14a and the original image.

The orthogonal transformation/quantization unit 14c is configured to perform orthogonal transformation processing and quantization processing on the residual signal generated by the residual signal generation unit 14b, and generate quantized transform coefficients. .

Here, the orthogonal transformation/quantization unit 14c determines whether or not to invert the basis used in the orthogonal transformation process based on the position of the reference pixel used when generating the predicted image determined by the intra prediction unit 14a. is configured to

For example, when the intra prediction unit 14a generates a predicted image using a reference pixel located on at least one of the right side and the bottom side (that is, a reference pixel adjacent to at least one of the right side and the bottom side), the orthogonal transform/ The quantization unit 14c is configured to perform orthogonal transform processing on the residual signal generated by the residual signal generation unit 14b after inverting at least one of the vertical and horizontal bases. .

On the other hand, when the intra prediction unit 14a does not generate a predicted image using the reference pixels located on either the right side or the bottom side, the orthogonal transformation/quantization unit 14c performs the residual signal generation unit 14
It is configured to apply orthogonal transform processing to the residual signal generated by b without inverting the basis.

For example, when the intra prediction unit 14a generates a predicted image using the reference pixels located on the left side and the lower side, the orthogonal transformation/quantization unit 14c performs orthogonal transformation processing after inverting the basis in the vertical direction. It may be configured to apply

Further, when the intra prediction unit 14a generates a predicted image using the reference pixels located on the right side and the upper side, the orthogonal transformation/quantization unit 14c performs orthogonal transformation processing after inverting the basis in the horizontal direction. It may be configured as

Furthermore, when the intra prediction unit 14a generates a predicted image using the reference pixels located on the right side and the lower side, the orthogonal transformation/quantization unit 14c reverses the bases in the vertical direction and the horizontal direction, It may be configured to perform conversion processing.

In addition, when the intra prediction unit 14a generates a predicted image using reference pixels located on at least one of the right side and the lower side, and the orthogonal transform processing to be applied is an asymmetric orthogonal transform processing (for example, DST ), the orthogonal transformation and quantization unit 14c performs the residual signal generation unit 1
4b may be configured to invert at least one of the vertical and horizontal bases used for orthogonal transform processing.

That is, even when the intra prediction unit 14a generates a predicted image using reference pixels located on at least one of the right side and the bottom side, the orthogonal transform processing to be applied is a symmetrical orthogonal transform processing (for example, DCT etc.), the orthogonal transformation/quantization unit 14c may be configured not to invert the basis used in the orthogonal transformation processing for the residual signal generated by the residual signal generation unit 14b. .

Further, when the intra prediction unit 14a generates a predicted image using reference pixels adjacent in three directions such as the lower side, the left side, and the upper side, the orthogonal transform/quantization unit 14c performs the residual signal generation unit 14
It may be configured not to invert the basis used for the orthogonal transform processing for the residual signal generated by b.

According to such a configuration, in the residual signal, since there is a high possibility that the signal strength is low both on the upper side and the lower side near the reference pixel, the encoding apparatus 1 processing amount can be reduced.

Further, when the intra prediction unit 14a generates a predicted image using reference pixels adjacent in three directions such as the right side, the left side, and the upper side, the orthogonal transform/quantization unit 14c performs the residual signal generation unit 14
It may be configured not to invert the basis used for the orthogonal transform processing for the residual signal generated by b.

According to such a configuration, in the residual signal, since there is a high possibility that the signal strength is low on both the right side and the left side near the reference pixel, by not performing the above-described inversion processing, the coding apparatus 1 The amount of processing can be reduced.

The inverse quantization unit/inverse orthogonal transform unit 14d performs the inverse quantization process and the inverse orthogonal transform process again on the quantized transform coefficients generated by the orthogonal transform/quantization unit 14c, and generates a residual signal. configured to generate

Here, when the orthogonal transform/quantization unit 14c inverts the base used in the orthogonal transform processing, the inverse quantization unit/inverse orthogonal transform unit 14d performs the inverse orthogonal transform processing after inverting the basis. configured to apply.

The local decoded image generation unit 14e generates a local decoded image by adding the predicted image generated by the intra prediction unit 14a to the residual signal generated by the inverse quantization unit/inverse orthogonal transformation unit 14d. It is configured.

The memory 15 is configured to retain locally decoded images generated by the sequential local decoded image generator 14 so as to be usable as reference images.

The entropy coding unit 16 is configured to perform entropy coding processing on the flag information including the intra prediction mode determined by the intra prediction mode determination unit 11 and the quantized transform coefficients, and to output a stream. there is

FIG. 3 shows a flowchart for explaining an example of the operation of the encoding device 1 according to this embodiment.

As shown in FIG. 3, in step S101, the encoding device 1 determines the optimum intra prediction mode to apply to the CU.

In step S102, the encoding device 1 determines whether to divide the CU into multiple TUs. If it is determined in step S102 that the CU is to be split into multiple TUs, the operation proceeds to step S103. On the other hand, if it is determined in step S102 that the CU is not split into multiple TUs, the operation proceeds to step S108.

When it is determined in step S103 that the direction of the intra prediction mode is the direction from the lower left to the upper right or the direction from the upper right to the lower left, this operation proceeds to step S10.
Proceed to 5. On the other hand, when it is determined in step S103 that the direction of the intra prediction mode is other than the direction from the lower left to the upper right and the direction from the upper right to the lower left, the operation proceeds to step S104.

In step S104, the encoding device 1 uses conventional HEVC as the encoding order described above.
adopt the raster scan order (Z type as shown in FIG. 8(a)) used in .

In step S108, the encoding device 1 encodes the TU to be encoded.
A predefined prediction is performed using the neighboring decoded reference pixels to the left and top of .

When it is determined that the direction of the intra prediction mode is from the lower left to the upper right (step S105), in step S106, the encoding device 1 sets TU#A3 (CU#A lower left TU in CU#A) → TU#A4 (lower right TU in CU#A) →
TU#A1 (top left TU within CU#A)→TU#A2 (top right TU within CU#A), or TU#A3 (bottom left TU within CU#A)→TU# A1 (upper left TU in CU#A) → TU#A4 (lower right TU in CU#A) → TU#A2 (upper right TU in CU#A) Adopt encoding order.

On the other hand, when it is determined that the direction of the intra prediction mode is not the direction from the lower left to the upper right (step S105), in step S111, the encoding device 1 sets TU#A2 (CU# Upper right TU in A) → TU#A4 (T at lower right in CU#A
U)→TU#A1 (upper left TU in CU#A)→TU#A3 (lower left TU in CU#A)
or TU#A2 (upper right TU in CU#A) → TU#A1 (CU#
TU#A4 (lower right TU in CU#A)→TU#A3 (lower left TU in CU#A). adopt.

In step S107, the encoding device 1 determines whether or not the reference pixel adjacent to the upper side of the TU to be encoded has been decoded. In step S107, if the decoding has been completed, the operation proceeds to step S109, and if the decoding has not been completed, the operation proceeds to step S110.

In step S109, the encoding device 1 encodes the TU to be encoded.
A predefined prediction is performed using the neighboring decoded reference pixels to the left and above and below of .

In step S110, the encoding device 1 encodes the TU to be encoded.
A predefined prediction is performed using the neighboring decoded reference pixels to the left and to the bottom of .

In step S112, the encoding device 1 determines whether or not the reference pixel adjacent to the left side of the TU to be encoded has been decoded. In step S112, if the decoding has been completed, the operation proceeds to step S113, and if the decoding has not been completed, the operation proceeds to step S114.

In step S113, the encoding device 1 encodes the TU to be encoded.
A predefined prediction is performed using the neighboring decoded reference pixels to the left, top and right of .

In step S114, the encoding device 1 encodes the TU to be encoded.
A predefined prediction is performed using the decoded reference pixels that are adjacent to the right and top of .

In step S115, the encoding apparatus 1 inverts the basis of the residual signal, performs orthogonal transform processing on the residual signal, and performs subsequent processing.

In step S116, the encoding device 1 performs orthogonal transform processing on the residual signal without inverting the basis, and performs subsequent processing.

According to the coding apparatus 1 according to the present embodiment, when a predicted image is generated using reference pixels located on at least one of the right side and the bottom side, the basis is inverted for the residual signal. , the increase in entropy can be reduced.

Further, the decoding device 3 according to the present embodiment converts the original image of each frame constituting the moving image into a CU
It is configured to be divided into and decoded. Also, the decoding device 3 according to this embodiment is configured to be able to divide a CU into a plurality of TUs, like the encoding device 1 according to this embodiment.

As shown in FIG. 4, the decoding device 3 according to this embodiment includes an entropy decoding unit 31, a decoding order control unit 32, a sequential local decoded image generation unit 33, and a memory .

The entropy decoding unit 31 is configured to decode transform coefficients, flag information, and the like from the stream output from the encoding device 1 . Here, the transform coefficients are quantized transform coefficients obtained by the encoding apparatus 1 as signals encoded by dividing the original image in units of frames into CUs. Also, the flag information includes accompanying information such as prediction mode.

The decoding order control unit 32 is configured to determine the decoding order of TUs within the CU based on the intra prediction mode.

Specifically, the decoding order control unit 32 uses a flag indicating whether or not the TU division output by the entropy decoding unit 31 has been performed (whether or not the CU is divided into a plurality of TUs) and the intra prediction mode. The direction is configured to determine the decoding order of the TUs within the CU.

For example, similar to the encoding order control unit 13, the decoding order control unit 32, when the CU is divided into a plurality of TUs and the direction of the intra prediction mode is from the lower left to the upper right, TU#A3 (lower left TU within CU#A) → TU#A4 (lower right TU within CU#A)
→ TU#A1 (upper left TU in CU#A) → TU#A2 (upper right TU in CU#A), or TU#A3 (lower left TU in CU#A) → TU# Predefined decoding in the decoding order of A1 (upper left TU in CU#A) → TU#A4 (lower right TU in CU#A) → TU#A2 (upper right TU in CU#A) It may be configured to perform decoding processing in order.

Further, similarly to the encoding order control unit 13, the decoding order control unit 32, when the CU is divided into a plurality of TUs and the direction of the intra prediction mode is from the upper right to the lower left, TU#A2 (top right TU within CU#A)→TU#A4 (bottom right TU within CU#A)→
The decoding order of TU#A1 (top left TU within CU#A)→TU#A3 (bottom left TU within CU#A), or TU#A2 (top right TU within CU#A)→TU#A1 Predetermined decoding in the decoding order of (upper left TU in CU#A) → TU#A4 (lower right TU in CU#A) → TU#A3 (lower left TU in CU#A) It may be configured to perform decoding processing in order.

The sequential local decoded image generation unit 33 uses the decoding order and the CU determined by the decoding order control unit 32.
is configured to generate a locally decoded image (a decoded image for each TU) based on the method of dividing into TUs.

Specifically, when the CU is divided into a plurality of TUs, the sequential locally decoded image generation unit 33 performs the quantization output by the entropy decoding unit 31 according to the decoding order determined by the decoding order control unit 32. A locally decoded image is generated by sequentially performing intra prediction, inverse quantization processing, and inverse orthogonal transform processing on the transformed transform coefficients.

As shown in FIG. 4, the sequential local decoded image generation unit 33 includes an intra prediction unit 33a, an inverse quantization/inverse transform unit 33b, and a decoded image generation unit 33c.

The intra prediction unit 33 a may be configured to generate a prediction image using the intra prediction mode output by the entropy decoding unit 31 according to the decoding order determined by the decoding order control unit 32 .

Specifically, when the CU is divided into a plurality of TUs and the direction of the intra prediction mode is from the lower left to the upper right, the intra prediction unit 33a determines TU #A3 (C
lower left TU in U#A) → TU#A4 (lower right TU in CU#A) → TU#A1 (CU#
A (upper left TU in A) → TU #A2 (upper right TU in CU #A), or T
U#A3 (bottom left TU in CU#A)→TU#A1 (top left TU in CU#A)→TU#
It is configured to generate a prediction image in a predetermined decoding order out of the decoding order of A4 (lower right TU in CU#A)→TU#A2 (upper right TU in CU#A). good too.

Here, as shown in FIGS. 2(c) and 2(d), the intra prediction unit 33a predicts TU#A1 (upper left TU in CU#A) whose adjacent lower reference pixel is decoded. and TU#A2
For (the upper right TU in CU#A), the predicted image may be generated using the decoded reference pixels adjacent to the left and lower sides.

Further, in the decoding device 3 according to the present embodiment, the intra prediction unit 33a can
and the direction of intra prediction mode (prediction direction) is from upper right to lower left, TU#A2 (upper right TU in CU#A) → TU#A4 (CU#
A) → TU#A1 (upper left TU in CU#A) → TU#A3 (lower left TU in CU#A), or TU#A2 (inside CU#A) upper right TU) → TU#
A1 (upper left TU in CU#A)→TU#A4 (lower right TU in CU#A)→TU#A3
The prediction image may be generated in a predetermined decoding order out of the decoding order (lower left TU in CU#A).

Here, the intra prediction unit 33a predicts TU#A in which the adjacent right reference pixel is decoded.
For 1 (upper left TU in CU#A) and TU#A3 (lower left TU in CU#A),
The prediction image may be generated using decoded reference pixels adjacent to the upper side and the right side.

Alternatively, the intra prediction unit 33a performs TU#A3 (the lower left TU in CU#A)→TU#A
4 (bottom right TU in CU#A)→TU#A1 (top left TU in CU#A)→TU#A2 (
upper right TU in CU#A), or TU#A3 (lower left TU in CU#A)
)→TU#A1 (upper left TU in CU#A)→TU#A4 (lower right TU in CU#A)→
When the decoding order of TU#A2 (upper right TU in CU#A) is used, the TU whose upper adjacent reference pixel has already been decoded (the TU located at the top of the divided TU group, In the example of FIG. 2, for TU#A1 and TU#A2), linear prediction using decoded reference pixels adjacent to the left side, upper side, or lower side of the TU is not performed in the common intra prediction direction in CU#A. It may be configured to perform predefined predictions such as interpolation.

The inverse quantization/inverse transform unit 33b performs inverse quantization processing and inverse transform processing (for example, inverse orthogonal transform processing) on the quantized transform coefficients output from the entropy decoding unit 31, thereby generating a residual configured to generate a signal;

For example, when the intra prediction unit 33a generates a predicted image using a reference pixel located on at least one of the right side and the bottom side (that is, a reference pixel adjacent to at least one of the right side and the bottom side), inverse quantization The inverse transform unit 33b is configured to generate a residual signal by inverting at least one of the bases in the vertical direction and the horizontal direction and then performing inverse orthogonal transform processing on the transform coefficients. there is

On the other hand, when the intra prediction unit 33a does not generate a predicted image using the reference pixels located on either the right side or the bottom side, the inverse quantization/inverse transform unit 33b does not invert the base. , to generate a residual signal by performing inverse orthogonal transform processing on the transform coefficients.

For example, when the intra prediction unit 33a generates a predicted image using the reference pixels located on the left side and the lower side, the inverse quantization/inverse transform unit 33b reverses the base in the vertical direction, and then may be configured to generate a residual signal by performing inverse orthogonal transform processing on the transform coefficients of .

Further, when the intra prediction unit 33a generates a predicted image using the reference pixels located on the right side and the upper side, the inverse quantization/inverse transform unit 33b reverses the base in the horizontal direction, The residual signal may be generated by performing inverse orthogonal transform processing on the transform coefficients.

Furthermore, when the intra prediction unit 33a generates a predicted image using the reference pixels located on the right side and the bottom side, the inverse quantization/inverse transform unit 33b reverses the bases in the vertical direction and the horizontal direction, , and may be configured to generate a residual signal by performing inverse orthogonal transform processing on the above-described transform coefficients.

In addition, when the intra prediction unit 33a generates a predicted image using the reference pixels located on at least one of the right side and the lower side, and the orthogonal transform processing to be applied is an asymmetric orthogonal transform processing (for example, DST ), the inverse quantization/inverse transform unit 33b is configured to invert the basis and then perform inverse orthogonal transform processing on the above transform coefficients to generate a residual signal. may

That is, even when the intra prediction unit 33a generates a predicted image using reference pixels located on at least one of the right side and the bottom side, the applied orthogonal transform processing is a symmetrical orthogonal transform processing (for example, DCT etc.), the inverse quantization/inverse transform unit 33b is configured to generate a residual signal by performing inverse orthogonal transform processing on the transform coefficients without inverting the basis. may

Further, when the intra prediction unit 33a generates a predicted image using reference pixels adjacent in three directions such as the lower side, the left side, and the upper side, the inverse quantization/inverse transform unit 33b performs It may be configured not to invert the basis used for the inverse orthogonal transform process.

In addition, when the intra prediction unit 33a generates a predicted image using reference pixels adjacent in three directions such as the right side, the left side, and the upper side, the inverse quantization/inverse transform unit 33b performs the inverse It may be configured not to invert the basis used for the orthogonal transform processing.

The decoded image generator 33c is configured to generate a local decoded image by adding the predicted image generated by the intra prediction unit 33a and the residual signal generated by the inverse quantization/inverse transform unit 33b. .

The memory 34 is configured to hold locally decoded images generated by the sequential locally decoded image generator 33 so as to be usable as reference images for intra prediction and inter prediction.

FIG. 5 shows a flowchart for explaining an example of the operation of determining the above-described decoding order by the decoding device 3 according to this embodiment.

As shown in FIG. 5, the decoding device 3 acquires an intra prediction mode from the stream output from the encoding device 1 in step S201.

In step S<b>202 , the decoding device 3 determines whether or not the CU is divided into a plurality of TUs based on flag information included in the stream output from the encoding device 1 . If it is determined in step S202 that the CU is divided into multiple TUs, the operation proceeds to step S203. On the other hand, in step S202, CU
is not divided into multiple TUs, the operation proceeds to step S205.

In step S205, the decoding device 3 performs predetermined prediction on the TU to be decoded using the decoded reference pixels adjacent to the left and upper sides of the TU.

In step S203, the decoding device 3 determines whether the direction of the intra prediction mode is the direction from the lower left to the upper right or the direction from the upper right to the lower left. When it is determined in step S203 that the direction of the intra prediction mode is the direction from the lower left to the upper right or the direction from the upper right to the lower left, the operation proceeds to step S206.

On the other hand, when it is determined in step S203 that the direction of the intra prediction mode is other than the direction from the lower left to the upper right and the direction from the upper right to the lower left, the operation proceeds to step S204.

In step S204, the decoding device 3 adopts the conventional raster scan order (Z type as shown in FIG. 8A) used in HEVC as the decoding order described above.

When it is determined that the direction of the intra prediction mode is the direction from the lower left to the upper right (step S206), in step S207, the decoding device 3 sets the above-described decoding order as follows:
TU#A3 (bottom left TU in CU#A)→TU#A4 (bottom right TU in CU#A)→TU
#A1 (upper left TU in CU#A) → TU#A2 (upper right TU in CU#A) in decoding order, or TU#A3 (lower left TU in CU#A) → TU#A1 ( Upper left TU in CU#A)→TU#A4 (Lower right TU in CU#A)→TU#A2 (Upper right TU in CU#A
), a predetermined decoding order is adopted.

On the other hand, when it is determined that the direction of the intra prediction mode is not the direction from the lower left to the upper right (step S206), in step S211, the decoding device 3 sets TU#A2 (within CU#A) as the decoding order described above. upper right TU) → TU#A4 (lower right TU in CU#A)
→ TU#A1 (upper left TU in CU#A) → TU#A3 (lower left TU in CU#A), or TU#A2 (upper right TU in CU#A) → TU# Predefined decoding in the decoding order of A1 (upper left TU in CU#A) → TU#A4 (lower right TU in CU#A) → TU#A3 (lower left TU in CU#A) Adopt order.

In step S208, the decoding device 3 determines whether or not the reference pixel adjacent to the upper side of the TU to be decoded has been decoded. In step S208, if the decoding has been completed, the operation proceeds to step S209; otherwise, the operation proceeds to step S209.
Proceed to 210.

In step S209, the decoding device 3 performs predetermined prediction on the TU to be decoded using the decoded reference pixels adjacent to the left side, upper side, and lower side of the TU.

In step S210, the decoding device 3 performs predetermined prediction on a TU to be decoded using decoded reference pixels adjacent to the left side and lower side of the TU.

In step S212, the decoding device 3 determines whether or not the reference pixel adjacent to the left side of the TU to be decoded has been decoded. In step S212, if the decoding has been completed, the operation proceeds to step S213, and if the decoding has not been completed, the operation proceeds to step S213.
Proceed to 214.

In step S213, the decoding device 3 performs predetermined prediction on the TU to be decoded using the decoded reference pixels adjacent to the left, upper and right sides of the TU.

In step S214, the decoding device 3 performs predetermined prediction on the TU to be decoded using the decoded reference pixels adjacent to the right and upper sides of the TU.

In step S215, the decoding device 3 generates a residual signal by inverting at least one of the bases in the vertical direction and the horizontal direction, and performing inverse orthogonal transform processing on the transform coefficients. process.

In step S216, the decoding device 3 generates a residual signal by performing inverse orthogonal transform processing on the transform coefficients without inverting the basis, and performs subsequent processing.

According to the decoding device 3 according to the present embodiment, when the predicted image is generated using the reference pixels located on at least one of the right side and the bottom side, the basis is inverted for the transform coefficients, and then the bases are inverted. Since it is configured to perform orthogonal transform processing, an increase in entropy can be reduced.

(Second embodiment)
6 and 7, the encoding device 1 and the decoding device 3 according to the second embodiment of the present invention are compared with the encoding device 1 and the decoding device 3 according to the above-described first embodiment. A description will be given focusing on the differences between the two.

In the encoding device 1 according to the present embodiment, when the intra prediction unit 14a generates a predicted image using reference pixels located on at least one of the right side and the bottom side, the orthogonal transformation/quantization unit 1
4c is configured to invert the residual signal generated by the residual signal generator 14b in at least one of the horizontal direction and the vertical direction, and then perform orthogonal transform processing.

For example, when the intra prediction unit 14a generates a predicted image using the reference pixels located on the left side and the lower side, the orthogonal transformation/quantization unit 14c generates the residual signal generated by the residual signal generation unit 14b. may be vertically inverted and then orthogonally transformed.

Further, when the intra prediction unit 14a generates a predicted image using the reference pixels located on the right side and the upper side, the orthogonal transformation/quantization unit 14c converts the residual signal generated by the residual signal generation unit 14b into It may be configured to perform orthogonal transformation processing after inverting it in the horizontal direction.

Furthermore, when the intra prediction unit 14a generates a predicted image using the reference pixels located on the right side and the lower side, the orthogonal transformation/quantization unit 14c generates the residual signal generated by the residual signal generation unit 14b. may be inverted vertically and horizontally and then orthogonally transformed.

In addition, when the intra prediction unit 14a generates a predicted image using reference pixels located on at least one of the right side and the lower side, and the orthogonal transform processing to be applied is an asymmetric orthogonal transform processing (for example, DST ), the orthogonal transformation and quantization unit 14c performs the residual signal generation unit 1
4b may be configured to invert the residual signal in at least one of the horizontal and vertical directions and then perform the orthogonal transform processing.

That is, even when the intra prediction unit 14a generates a predicted image using reference pixels located on at least one of the right side and the bottom side, the orthogonal transform processing to be applied is a symmetrical orthogonal transform processing (for example, DCT etc.), the orthogonal transformation/quantization unit 14c may be configured to perform orthogonal transformation processing without inverting the residual signal generated by the residual signal generation unit 14b.

Further, when the intra prediction unit 14a generates a predicted image using reference pixels adjacent in three directions such as the lower side, the left side, and the upper side, the orthogonal transform/quantization unit 14c performs the residual signal generation unit 14
It may be configured to perform orthogonal transform processing without inverting the residual signal generated by b.

Further, when the intra prediction unit 14a generates a predicted image using reference pixels adjacent in three directions such as the right side, the left side, and the upper side, the orthogonal transform/quantization unit 14c performs the residual signal generation unit 14
It may be configured to perform orthogonal transform processing without inverting the residual signal generated by b.

FIG. 6 shows a flowchart for explaining an example of the operation of the encoding device 1 according to this embodiment.

As shown in FIG. 6, the operations of steps S301 to S314 are performed in step S10 shown in FIG.
1 to S114.

In step 315, the encoding device 1 performs orthogonal transform processing without inverting the above residual signal, and performs subsequent processing.

In step 316, the encoding apparatus 1 inverts the above residual signal in at least one of the horizontal direction and the vertical direction, performs orthogonal transform processing, and performs subsequent processing.

According to the encoding device 1 according to the present embodiment, when a predicted image is generated using reference pixels located on at least one of the right side and the bottom side, the residual signal is oriented in at least one of the horizontal direction and the vertical direction. Since it is configured to perform orthogonal transformation processing after inversion, an increase in entropy can be reduced.

In the decoding device 3 according to the present embodiment, when the intra prediction unit 33a generates a predicted image using reference pixels located on at least one of the right side and the bottom side, the inverse quantization/inverse transform unit 33
b is configured to invert in at least one of the horizontal and vertical directions a signal obtained by performing inverse orthogonal transform processing on the transform coefficients.

For example, when the intra prediction unit 33a generates a predicted image using the reference pixels located on the left side and the lower side, the inverse quantization/inverse transform unit 33b performs inverse orthogonal transform processing on the transform coefficients. may be configured to invert the signal obtained in the vertical direction.

Further, when the intra prediction unit 33a generates a predicted image using the reference pixels located on the right side and the upper side, the inverse quantization/inverse transform unit 33b performs inverse orthogonal transform processing on the transform coefficients. It may be arranged to horizontally invert the resulting signal.

Furthermore, when the intra prediction unit 33a generates a predicted image using the reference pixels located on the right side and the lower side, the inverse quantization/inverse transform unit 33b performs inverse orthogonal transform processing on the transform coefficients. may be configured to vertically and horizontally invert the signal obtained in .

In addition, when the intra prediction unit 33a generates a predicted image using the reference pixels located on at least one of the right side and the lower side, and the orthogonal transform processing to be applied is an asymmetric orthogonal transform processing (for example, DST ), the inverse quantization/inverse transform unit 33b may be configured to invert a signal obtained by performing inverse orthogonal transform processing on the transform coefficients.

That is, even when the intra prediction unit 33a generates a predicted image using reference pixels located on at least one of the right side and the bottom side, the applied orthogonal transform processing is a symmetrical orthogonal transform processing (for example, DCT etc.), the inverse quantization/inverse transform unit 33b may be configured not to invert the signal obtained by performing the inverse orthogonal transform process on the transform coefficients described above.

Further, when the intra prediction unit 33a generates a predicted image using reference pixels adjacent in three directions such as the lower side, the left side, and the upper side, the inverse quantization/inverse transform unit 33b performs inverse orthogonal transform on the transform coefficients. It may be configured not to invert the signal obtained by performing the processing.

Further, when the intra prediction unit 33a generates a predicted image using reference pixels adjacent in three directions such as the right side, the left side, and the upper side, the inverse quantization/inverse transform unit 33b performs inverse orthogonal transform processing on the transform coefficients. may be configured so as not to invert the signal obtained by applying

FIG. 7 shows a flowchart for explaining an example of the operation of the decoding device 3 according to this embodiment.

As shown in FIG. 7, the operations of steps S401 to S414 are performed in step S20 shown in FIG.
1 to S214.

In step 415, the decoding device 3 performs subsequent processing without inverting the signal obtained by performing the inverse orthogonal transform processing on the transform coefficients.

In step 416, the decoding device 3 inverts in at least one of the horizontal direction and vertical direction the signal obtained by performing the inverse orthogonal transform processing on the transform coefficients, and then performs subsequent processing.

(Other embodiments)
As noted above, the present invention has been described through the above-described embodiments, but the statements and drawings forming part of the disclosure in such embodiments should not be understood to limit the present invention. From such disclosure, various alternative embodiments, implementations and operational techniques will become apparent to those skilled in the art.

Moreover, although not particularly mentioned in the above-described embodiment, a program may be provided that causes a computer to execute each process performed by the above-described encoding device 1 and decoding device 3 . Also, such a program may be recorded on a computer-readable medium. Such programs can be installed on a computer using a computer readable medium. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, but may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.

Alternatively, a chip configured by a memory storing a program for realizing at least part of the functions in the encoding device 1 and the decoding device 3 described above and a processor executing the program stored in the memory may be provided. good.

1 Encoding device 11 Intra prediction mode determination unit 12 TU division determination unit 13 Encoding order control unit 14 Sequential local decoded image generation unit 14a Intra prediction unit 14b Residual signal generation unit 14c Orthogonal transformation/ Quantization unit 14d: Inverse quantization unit/inverse orthogonal transformation unit 14e: Local decoded image generation unit 15: Memory 16: Entropy encoding unit 3: Decoding device 31: Entropy decoding unit 32: Decoding order control unit 33: Sequential local decoding Image generating unit 33a...Intra prediction unit 33b...Inverse quantization/inverse transform unit 33c...Decoded image generating unit 34...Memory

Claims (2)

A decoding device for decoding a target block encoded by dividing an original image in units of frames constituting a moving image,
An intra prediction unit that generates a predicted image corresponding to the target block using an intra prediction mode;
an inverse transform unit that performs inverse transform processing on transform coefficients corresponding to the target block;
The inverse transform unit
Mode determination processing including determining whether the direction of the intra prediction mode applied to the target block by the intra prediction unit is a direction from the lower left to the upper right, and determining whether it is a direction from the upper right to the lower left;
an inversion control process for controlling an inversion process for inverting a signal obtained by performing the inverse transform process on the transform coefficient in a predetermined direction based on the determination result of the mode determination process;
The inversion control process controls the inversion process further based on the position of the reference pixel referred to when the intra prediction unit generates the predicted image,
The inversion control process inverts the signal in at least one of the horizontal direction and the vertical direction when the intra prediction unit generates the predicted image using reference pixels positioned at least one of the right side and the bottom side. A decoding device characterized by: A program for causing a computer to function as the decoding device according to claim 1.

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